1. Field of the Invention
The present invention relates to an etch resist solution and a method of fabricating a thin film pattern for a display panel using the etch resist solution. More particularly, the present invention relates to improving the life of a blanket to reduce the cost and improve reliability in forming the thin film pattern.
2. Discussion of the Related Art
Flat panel display devices are popular because they are smaller and lighter than cathode ray tube devices. Examples of flat panel display devices include liquid crystal display devices, field emission display devices, plasma display panel devices and electroluminescence (EL) displays.
In a liquid crystal display device, a picture image is displayed by controlling the transmission of light through liquid crystal. Light transmittance is controlled by using an electric field. Thus, liquid crystal display devices may include a liquid crystal display panel provided with liquid crystal cells, typically arranged in a matrix, and a driving circuit for driving the liquid crystal display panel.
The liquid crystal display panel may include a thin film transistor array substrate, a color filter array substrate, a spacer located between the two substrates to maintain a cell gap, and a liquid crystal filled in the cell gap. The thin film transistor array substrate and the color filter array substrate face each other.
The thin film transistor array substrate may include gate lines, data lines, and thin film transistors formed at portions of the gate lines and the data lines that cross each other. The thin film transistors serve as switching devices. The thin film transistor array substrate may also include pixel electrodes formed in a unit of liquid crystal cell and connected with the thin film transistors. An alignment film may also be deposited on the substrate to cover the above elements. The gate lines and the data lines are supplied with signals from driving circuits through their respective pad portions. The thin film transistors supply pixel signals, supplied to the data lines, to the pixel electrodes in response to scan signals supplied to the gate lines.
The color filter array substrate may include color filters formed in a unit of liquid crystal cell, a black matrix for distinguishing the color filters from one another and reflecting external light, a common electrode commonly supplying a reference voltage to the liquid crystal cells, and an alignment film deposited on the above elements.
The thin film transistor array substrate and the color filter array substrate may be separately fabricated and thereafter bonded to each other. After the substrates are bonded, liquid crystal material is injected between the bonded substrates and the substrates are then sealed. Thus, the related art liquid crystal display panel is completed.
Thin film patterns within the related art liquid crystal display panel may be formed by photolithography processes and etching processes.
Photolithographic processing includes multiple processes, such as exposure, developing, cleaning and inspection. These processes increase the fabricating cost of the liquid crystal display panel. Accordingly, a thin film patterning process may be performed using a reverse resist printing process instead of the photolithography process.
FIG. 1 illustrates a related art reverse resist printing apparatus.
As shown in FIG. 1, the related art reverse resist printing apparatus includes a roll type printing roller 10 in which a blanket 15 is wound, an etch resist solution injector 12 that injects an etch resist resin solution 14a, and an engraved printing plate 20. The engraved printing plate 20 includes a groove 20a having the same pattern as a thin film pattern to be formed and a protrusion 20b. The blanket 15 may be made of polydimethylsiloxane (PDMS).
In the related art reverse resist printing apparatus, after an etch resist solution 14a injected from the etch resist solution injector 12 is coated on the blanket 15 wound on the printing roller 10, the etch resist solution 14a is transferred onto the protrusions 20b only from the printing roller 10. Subsequently, an etch resist pattern 14b is formed on the printing roller 10 and is a desired thin film pattern. This thin film pattern remains on the printing roller 10 and is then transferred onto a substrate, so that an etch resist pattern is formed on the substrate.
The etch resist solution 14a used for the reverse resist printing apparatus may include a base polymer such as novolac, a carrier solvent, a printing solvent, a surfactant, etc. The etch resist solution 14a is injected from the etch resist solution injector 12.
A carrier solvent is a solvent used to uniformly coat the etch resist solution 14a on the blanket 15 by lowering the viscosity of the etch resist solution 14a. 
The printing solvent also affects the viscosity of the etch resist solution 14a coated on the blanket 15 and allows the solution 14a to print on the printing plate 20 or the substrate.
A surfactant is a material used to lower the surface tension of the etch resist solution 14a and the surface tension of a surface so that the solution 14a may adhere to the surface.
If a coating process is performed using the aforementioned etch resist solution 14a and the blanket 15 made of PDMS, the solvent of the etch resist solution 14a permeates into the blanket 15 and causes swelling of the blanket 15. Thus, the printing process cannot be performed exactly. The reliability in forming a thin film pattern is decreased and the life of the blanket 15 is remarkably reduced.